This invention relates to slide-type fasteners.
An interesting account by Lewis Weiner of the development of slide fasteners from their invention by Elias Howe in 19851 is to be found in "Scientific American", June 1983, pp. 122-129.
Among the fasteners made by techniques described by Mr Weiner are heavy duty, weatherproof fasteners for harsh environment clothing. Since, however, they consist of individual teeth carried on tapes (stringers) joined side by side, with the teeth intermeshing, by a slide, weatherproofing is problematical. It is a matter of effectively sealing, as by rubberising, the gaps between the teeth as best as one can. No completely satisfactory method of doing this has been found, and the usual resort, for weatherproofing, is to have a flap which covers the fastener and which is secured by a Velcro (RTM) type fastener.
Another problem with such fasteners is their tendency to jam by teeth becoming displaced or by intrusion of a thread from the garment or a frayed stringer.
One other type of slide fastener not mentioned in Mr Weiner's account comprises intermeshing elongate beads and recesses formed in a polyvinyl chloride or other plastics material film. Such a slide fastener is not extensively used, being mainly found on document wallets and pouches where it is moulded integrally. Various attempts to improve upon this type of continuous head fastener are mentioned in the patent literature, including German Patent Publication 2341452, 2656045 and 2701590 which involve various complicated profiles intended to effect clamping or tongue-and-groove like actions. They all evidently suffer from the disadvantage that the very flexibility that permits the two halves to be engaged also enables the halves to deform under tension forces therebetween so that they can disengage in ordinary use.
For clothing and most other applications fasteners comprised of individual teeth mounted on tapes or metal or plastic wire-formed teeth woven or otherwise embodied into tapes are preferred on account of their positive engagement when fastened.
The present invention provides an improved slide fastener of this continuous bead type not subject to the problems aforementioned.